Reese Witherspoon's birthday was quite the celebration. The actress rang in the big 4-0 in Los Angeles Saturday night (March 19) at the Warwick and her celebrity guest list included Keith Urban, Taylor Swift, Kate Hudson and Jennifer Aniston.

During the night, Witherspoon got on the stage and sang "Sweet Home Alabama" with the help of Urban on guitar. Dressed in a long-sleeved glittery ensemble and heels, Witherspoon was all smiles as she sang into the microphone and pointed to the crowd to sing along with her.

Vanity Fair fashion writer Derek Blasberg captured the moment on Instagram. He captioned the clip by writing, "You can take the girl out the south, but you can't take Sweet Home Alabama out the girl! HAPPY BIRTHDAY."

Witherspoon starred in the film Sweet Home Alabama in 2002, in which she played the lead role of Melanie Carmichael, a designer from Alabama trying to make it in New York City.

Swift also performed for Witherspoon. The singer sang her hit "Shake It Off" while Urban accompanied on guitar, as seen in the video below.

When Urban isn't playing the role of judge and advisor on American Idol's final season, he's putting the finishing touches on his upcoming album Ripcord. The country singer and guitar slinger recently revealed the release date of his eighth studio album. Ripcord will be available May 6.

“Ripcord is almost done — and it’s been an exhilarating journey,” Urban says in a press release. “Getting to work with so many new musicians and writers and co-producers has been a divine experience for me — and I can’t wait for everyone to hear it!”

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